Conventionally, inverter driving becomes common in an air conditioner. In an inverter and an electric motor connected to the inverter, a carrier noise that is a noise caused by switching of switching elements occurs due to an influence of a carrier frequency. A noise level of the carrier noise is different according to the carrier frequency. As a measure of reducing the carrier noise, there is a method of using an acoustic absorbent or an acoustic insulator in order to reduce noises around the carrier frequency. Further, Patent Literature 1 listed below discloses a technique for an electric-motor driving device that achieves quieting effect by setting the carrier frequency to a high frequency beyond the human audible band.